The present disclosure relates to flexible covers or tarping systems for open-topped containers and particularly concerns a mechanism for restraining the flexible cover or tarp against the container.
Many hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. In a typical dump truck application, the open-topped container is referred to as the “dump body” of the truck. The dump body is used to haul a variety of load material, such as gravel and the like, as well as organic materials, such as grain or produce. Upon reaching the dumping site, the dump truck tilts the dump body to evacuate the load material from the dump body.
Depending upon the nature of the load material stored in the open-topped container, it is often desirable to provide a cover for the container. A cover is particularly valuable for covering the dump body of a dump truck when dump truck is in transit. Rigid covers are well known that may be hinged from one end of the container body and pivoted from an open to a closed position. While rigid covers may be acceptable for stationary containers, the same is usually not true for containers associated with land-traversing vehicles. Accordingly, rigid covers have given way to flexible cover systems.
Flexible cover systems utilize a flexible tarpaulin that can be drawn from a stowed position at one end of the container, to a deployed position covering the open top of the container. The flexible tarpaulin is preferable for dump trucks, because it can be easily stowed when the cover is not needed, such as during times when the dump body is being loaded and emptied. In addition, flexible cover systems are generally easier to deploy than rigid covers.
A variety of flexible cover systems have been developed that are geared toward particular hauling vehicle applications. One such tarping system is the Easy Cover® Tarping System manufactured and sold by Aero Industries, Inc. An example of one form of the Easy Cover® Tarping System is shown in FIG. 1. The system includes a U-shaped bail member 22 that is connected at a pivot mount 25 to the base of the container body 13 on the vehicle 10. A horizontal section 27 of the bail member 22 is attached to the tarp 16. The system also includes a U-shaped tensioning bow member 30 that is connected at a pivot mount 32 to the bail member 22. The tarp 16 is positioned between a horizontal section 34 of the tensioning bow member 30 and the container body 13. The tarp 16 can be preferably stowed by winding onto a tarp roller 19 at the forward end of the vehicle, which causes the tarp to slide under the horizontal section 34 of the tensioning bow member 30 as the bail member 22 pivots toward the front of the container body 13.
The system includes a variety of configurations that permit manual or powered deployment of the tarp over the open top of the container. In one typical installation, the pivot mount 25 includes a torsion spring pack that is biased to rotate the bail member 22 in a clockwise direction, as shown in FIG. 1, to pull the tarp 16 over the top of the container 13. The tarp roller 19 is biased to resist this rotation of the bail member 22. In some versions, a manual crank rotates the tarp roller 19 to allow the tarp 16 to unfurl under the torsion force of the spring pack. In other versions, a motor controls the rotation of the tarp roller. The manual crank or motor are rotated in the opposite direction to pull the bail member 22 toward the front of the container body 13 and to thereby stow the tarp 16.
One problem that is faced with tarping systems of the type shown in FIG. 1 is the effect of airflow or wind on the tarping system as the vehicle is traveling. In particular, the tarpaulin 16 is affected in a number of ways by the airflow associated with the traveling vehicle. This problem becomes especially acute at high speeds. In particular, the front end of the vehicle creates turbulent airflow that travels along the length of the container body 13. The turbulence, which can be manifested by air vortices along the top of the container body 13, has a tendency to lift the flexible cover 16 away from the top of the body.
Another problem facing the above-described tarping system is road vibration and shock, which can cause the bail member 22 and the tensioning bow member 30 to bounce on the container body 13 when the tarp 16 is deployed. This problem is especially noticeable for systems including the tensioning bow member 30, the position of which is maintained by only the weight of the tensioning bow member 30.
Movement of the tarp 16, the bail member 22, and the tensioning bow member 30 due to wind and vibration may have a deleterious effect is on the flexible cover system. The constant flapping and bouncing can gradually wear the tarp and the cover system components, which decreases the longevity of the cover system. In addition, when the tarp 16 is dislodged from its deployed position, the contents of the container body 13 are at risk of expulsion.
In order to address this problem, various systems have been devised to bias the tarp against the container body. In one common cover system, a web of cords is deployed over the tarp 16 along the length of the container body 13. The ends of the cords can be attached to mounts affixed to the side of the body 13. Whereas other cover systems rely on a complicated array of mechanical, electrical, and/or hydraulic structures to apply a constant tension along the length of the tarp 16. In most cases, however, these cover systems do not adequately restrain the bail/bow members 22, 30 or the tarp 16.
Another system is disclosed in U.S. Pat. No. 8,267,461 that contemplates a tarping system 100 for an open-topped container 120 includes a bail member, shown as a U-shaped tensioning bow member 102, and another U-shaped bail member 104, as shown in FIG. 2. The bail member 104 includes two legs 105 with end portions of the legs 105 connected to the bottom of the container 120 by a pair of torsion spring packs 134 (only one of which is illustrated in FIG. 2). The tensioning bow member 102 includes a pair of legs 103 and a horizontal mid-section 112. As described in the '461 Patent, the disclosure of which is incorporated herein by reference, the end portion of each leg 103 is connected to the legs 105 of the bail member 104 by another pair of torsion spring packs 108 (only one of which is illustrated in FIG. 2). The spring packs 108 include a housing 109 for one or more biasing springs (not shown) that is engaged to a mount 132 for fixing the spring packs to the bail member. The spring packs 108 form a hold-down assembly that is configured to bias the horizontal section 112 of the tensioning bow member 102 against the tarp 124 and an upper edge 128 of the container 120 (or a load carried by the container, if the load is positioned above the upper edge 128) to restrain movement the tensioning bow member 102. Accordingly, the horizontal section 112 is positioned against the tarp 124 by a force greater than just the weight of the bail member 102. The spring packs 108 exert a biasing force that is greater than the force exerted upon the tensioning bow member 102 by normal wind and/or gravity, among other effects.
Most prior approaches to maintaining the tarp against the container body either require manual intervention or sophisticated powered components. Accordingly, there remains a need for an improved tarping system having a tensioning bow member which is less prone to the wind and vibrations associated with a moving container.